Fluid heating



Aug. 29, 1950 c. L. NORTON, JR 2,520,164

FLUID HEATING Filed July 4, 1944 4 Sheets-Sheet 1 IN V EN TOR.

C [1 (If! ESLNorionJzt A TTORNE Y 1950 c. L. NORTON, JR 2,520,164

FLUID HEATING Filed July 4, 1944 4 Sheets-Sheet 2 85 IN V EN TOR.

Char/e5 L .Norzon, Jr

W A TTOPNEY Aug. 29, 1950 c. NORTON, JR 2,520,164

FLUIDHEATING Filed July 4, 1944 4 Sheets-Sheet s 9 INVENTOR.

Char/es 1. Norton, Jr

A TTORNE Y C. L. NORTON, JR

Aug. 29, 1950 FLUID HEATING 4 Sheets-Sheet 4 Filed July 4, 1944 INVENTORCar/asl. Nada/7, Jk

ATTORNEY Patented Aug. 29, 1950 FLUID HEATING Charles L. Norton, Jr.,New York, N. Y., assignor to The Babcock & Wilcox Company, Rockieigh.

N. J., a corporation of New Jersey Application July 4, 1944, Serial No.543,441

11 Claims.

My present invention relates to the construction and operation of fluidheating apparatus of the general type disclosed ir. a copendingapplication of E. G. Bailey and R. M. Hardgrove, Serial No. 502,580,filed Sept. 16, 1943, now Patent No. 2,447,306 of August 17, 1948, inwhich a fluent mass or column of refractory heat transfer material issubstantially continuously circulated downwardly through superposedheating and cooling chambers or zones in which the heat transfermaterial is first heated to a high temperature by the passage of aheating fluidin heat transfer relation therewith, and then cooled byheat transfer contact with a fluid to be heated, the heat transfermaterial then being returned to the upper end of the heating zone bysuitable external elevating means. Fluid heating appa ratus of this typeare frequently referred to as "pebble heaters, although a wide range ofheat transfer materials other than pebbles can be used therein.

Apparatus of the character described has been found suitable forcontinuously heating fluids to final temperatures considerably higherthan the fluid temperatures for which ordinary steel or alloy steeltubes can be safely and economically used. The final temperature of theheated fluid is mainly dependent upon the maximum tem-.

perature of the heat transfer material in the cooling zone and the timeof heat transfer contact of the fluid to be heated with the heattransfer material. The cross-sectional flow area for the mass of heattransfer material should be designed to provide uniform distribution ofthe heating and heated fluids therein and avoid overheating of parts ofthe descending mass of heat transfer material, thus maintainingsubstantially uniform temperature conditions throughout each level ofthe mass. High capacity operation depends upon the maximum flow velocitypermissible of the fluid to be heated through the mass of heat transfermaterial without excessive lifting and carryover of the heat transfermaterial with the outgoing heated fluid. A further desirable operatingcharacteristic is to have the heat transfer material discharging fromthe cooling zone at a temperature at which it is not subjected to athermal shock sufficient to crack or rupture the pieces of heat transfermaterial and at which the heat transfer material can be safely handledby metallicfeeding and elevating means without causing binding andseizing of such metal parts due to excessive thermal expansion. A lowentrance temperature and counterflow of a fluid to be 2 heated istherefore normally required to insure a suitable discharge temperatureof the heat transfer material. The resulting low entrance temperaturefor the heat transfer material and low exit temperature of the heatingfluid provides a high thermal efflciency for the apparatus and theheating process.

The general object of my invention is the provision of an improvedmethod and apparatus of the character described for continuously heatinga fluid at relatively high capacities to a uniform final temperature ina temperature range whose upper limit is dependent only upon thephysical limitations of the heat transfer material and heater wallrefractories employed, While maintaining little or no mixing of thefluid being heated with the fluid used for heating the heat transfermaterial. A further and more specific object is the provision of animproved construction of a pebble heater unit which is characterized bya fluid outlet construction providing a uniform discharge of the heatedfluid, a substantial reduction in the carryover of heat transfermaterial with the outflowing fluid, and a minimum heat radiation lossfrom the throat section of the heater. A further specific object is theprovision ,of improved separating means for eliminating dust andundersize pieces of heat transfer material from the unit. A furtherspecific object is the provision of an improved mechanism forcontrolling the discharge of a fluent mass of solid material from achamber under a positive pressure, such as the discharge of heattransfer material from the cooling zone of the apparatus described,while maintaining an effective gas seal at the lower end of the chamber.A further specific object is the provision of an improved mechanism forcontrolling the discharge of a fluent mass of solid material from achamber under a positive pressure, such as in a pebble heater of thecharacter described, which insures a continuous discharge of the solidmaterial from the chamber while maintaining an effective gas seal at thedischarge end of the chamber. A further specific object is the provisionof a multiple fluid heater construction and arrangement for securing afinal temperature of the fluid being heated substantially higherthanthat obtainable in a single unit of similar construction, wh.lemaintaining the heat transfer material discharging from each unit a partof this specification. For a better understanding of the invention, itsoperating advantages and specific objects attained by its use, referenceshould be had to the accompanying drawings and descriptive matter inwhich I have illustrated and described preferred embodiments of myinvention.

Of the drawings:

Fig. 1 is a somewhat diagrammatic elevation of a multiple fluid heaterunit constructed in accordance with my invention;

Fig. 2 is an enlarged sectional elevation of a .portion of one of thefluid heater units shown in Fig. 1;

Figs. 3, 4 and are horizontal sections taken on the lines 3--3, 44, and5-5. respectively, of Fig. 2;

Fig. 6 is an enlarged sectional elevation of the solid materialdischarge mechanism shown in Figs. 1 and 2;

Fig. '7 is a horizontal section taken on the line 1-1 of Fig. 6; and ig.8 is a partly diagrammatic sectional elevation of a modified form ofsolid material discharge mechanism.

In the fluid heater construction illustrated in Figs. 1-7, each pebbleheater unit has a vertically elongated fluid tight metal casing ill ofcircular cross-section lined with an annular wall of suitable hightemperature refractory material II. The fiuid heater interior is dividedinto an upper chamber l2 and a lower chamber I3 connected by avertically elongated uninterrupted throat passage ll of substantiallyreduced crosssection. The chambers l2 and i 3 and throat I are normallyfilled to the levels indicated with a continuous fiuent mass or columnof refractory heat transfer material l5 of a character hereinafterdescribed.

A heat transfer material inlet pipe I6 is connected to the upper part ofthe chamber l2 and a heating gas outlet pipe ll, controlled by a valvel8, opens centrally into the conical top IQ of the chamber. The materialinlet pipe 16 discharges into the lower portion of an auxiliary heatingas outlet pipe 20, which opens into the chamber I 2. A substantiallyannular combustion chamber 25 is formed by an enlarged section of thecasing l0 around the lower part of the chamber l2, As shown in Figs. 2and 5, the inner side of the combustion chamber is formed by an annularbridge wall 26 extending upwardly for part of the height of the' chamberand over which flow the heating gases generated by the combustion of anysuitable fuel in the surrounding combustion space. As shown, premixedair and gas burner nozzles 21 are arranged at diametrically oppositepoints and substantially tangential to the combustion chamber 25. Eachnozzle 21 is supplied by a valve controlled fuel pipe 28 and an aircasing 29 to which a secondary air supply pipe 30 is connected. Theignited mixture of fuel and air discharges through a burner block I intothe combustion chamber 25 under a positive pressure, with the heatinggases generated flowing over the top of the bridge wall 26 and through acircular series of inwardly tapering gas inlet ports 32 formed betweenwedge shaped firebrick 33 and openinginto the lower part of the chamberl2. The flrebrick 33 extend substantially the same height as the bridgewall 26 and form the corresponding portion of the wall of the chamberl2. The chamber 12 is formed with an inverted conical bottom sectionextending from the lower end of the ports 32 to the top of the throatpassage It. With this arrangement the heat transfer material in thechamber l2 tends to fiow outwardly through the gas ports 32 against thebridge \vall until the material assumes its normal angle of repose, thusproviding a subdivision of the inlet ports 32 facilitating distributionof the entering heating gases throughout the horizontal area of thechamber l2. The chamber i2 is flared outwardly nea the normal top of themass of material I5 therein to reduce the gas flow velocity in, andthereby the lifting effect on, the upper portion of the mass.

The lower chamber I3 is shown as of substantially uniform circularcross-section from its upper end to a point spaced from its lower end,the lower end portion of the chamber being downwardly tapered anddefined by an inverted frusto conical metal screen 35. The lower part ofthe casing I0 surrounding the screen 35 is downwardly tapered in a cone36, having a bottom discharge opening 31 which is spaced below the openlower end of the screen 35 to permit any heat transfer material passingthrough the screen to reach the outlet 31. The parts 35 and 36 cooperateto define an annular fiuid inlet chamber 38 to which one or more valvecontrolled fluid supply pipes 39 are connected for the admission of afluid to be heated under a positive pressure. The upper end of the lowerchamber I3 is a flat firebrick arch in which a multiplicity of radialnarrow outlet slots 40 are formed in wedge shaped firebrick 4|, as shownin Figs. 2 and,4. The inner ends of the firebrick 4| are interlockedwith one or more ceramic tile members 42 defining the downwardly flaringthroat passage M. An annular fluid outlet duct 43 surrounds the tile 42and into which open the outlet slots 40. One or more fiuid dischargepipes 44 are connected to the duct 43.

A relatively wide range of refractory materials can be used as the heattransfer material I5, the material chosen depending upon the operatingconditions to be maintained. In general the material selected shouldhave a high strength, hardness, resistance to thermal shock, and ahigh'softening temperature. Such materials may be ceramic refractoriesor corrosion resistant alloys and alloy steels, in small pieces ofregular or irregular shape, such as sized grog, pebbles or crystals ofmullite, silicon carbide, alumina, or other refractories. As disclosedin said copending application of E. G. Bailey et al., substantiallyspherical pellets of uniform shape and size and formed of a mixture ofcalcined Georgia kaolin, raw Georgia kaolin and a binder, fired to2850-3000 F. have been successfully used. The pellets are made of adiameter small enough to minimize thermal shocks and impact stresses,and to provide a large amount of heat transfer surface, and yet largeenough to withstand the desired gas velocities through the pellet masswithout lifting. Pebble diameters and r'e" have been found suitable.

The downward flow of heat transfer material through the upper chamberl2, throat I 4, and lower chamber i3, is controlled by a pressuretightfeeder receiving material from the pellet outlet 31, while maintaining afluid seal on the lower end of the chamber l3. The outlet pipe 31 opensinto a small fluid-tight expansion chamber 50 constructed to provide aspace above the pellets at their normal angle of repose therein. Theexpansion chamber 50 has a bottom outlet pipe 5| provided with anadjustable sleeve extension 53 having a sharp-edged lower enddetermining the etIective position of the outlet in a subjacent valvechamber 52. The feeder mechanism is constructed to provide a periodicischarge of a small amount of pellets from the lower end of the sleeve53. The mechanism for this purpose comprises a valve member 55 in thechamber 52 having a concave upper surface, preferably in the form of abowl or cup having an inner central conical portion 56. The cone 56 actsto deflect the pellets outwardly on the valve member and facilitates itsmovement upwardly and the discharge of pellets therefrom. The cup valvemember 55 is vertically movable by means of a rod 51 between an upperposition shown in full lines in Fig. 6 at which the normal angle ofrepose of the pellets onthe upper surface of the valve member is greaterthan the angle formed between the outer periphery of the valve memberand the lower end of the sleeve 53, so that the pellets do not tend toflow over the periphery of the valve member when the latter is in itsupper position, and a lower position indicated in broken lines at which'the angle between the periphery of the valve member and the bottom ofthe sleeve will be greater than the angle of repose of the pellets onthe valve memher, so that a gravity flow of the pellets over theperiphery of the valve member can take place when the valve is moved tothis position. The flow of pellets is thus dammed when the cupshapedvalve member 55 is moved to its upper position without requiring anycontact between the valve member and the lower end of the sleeve whichmight tend to crush pellets therebetween.

The valve chamber 52 has a. central valve controlled bottom outlet 58opening into a third chamber 59. The passage of pellets from the chamber52 through the outlet 58 into the chamber 59 is controlled by avertically movable bell valve member 60 slidable relative to the rod 51in the chamber 59 and mounted on a hollow rod 6| surrounding the rod 51.The valve 60 is timed to open after the cup valve member 55 reaches itsupper position and stops the pellet flow from the lower end of thesleeve 53. The downward movement of the valve 60 permits the pelletsaccumulated in the bottom of the chamber 52 to drop into the chamber 59which has a discharge opening 62 concentric with the opening 58 andclosed by a bell valve member 64 similar to the valve member 60. Thevalve 64 surrounds and is movable relative to the operating rods 51 and6| and is mounted on a third hollow rod 65 surrounding the rods 51 and6|. The opening of the valve member 64 permits the pellets to drop intoan inclined discharge pipe 66. The valve 64 is normally closed when thevalve 60 is open and vice versa to minimize fluid leakage from and thuspreserve the fluid pressure conditions in the chamber I3. The describedvalve parts are coaxially arranged with the operating rods extendingthrough a guide bearing in the discharge pipe 66.

The cup valve member 55 and bell valves 60 and 64 are intermittentlyoperated to effect a fluid seal at all times on the lower end of thechamber I3. The operating mechanism for this purpose consists of a pairof cam members 10 and 1| rotated by a shaft 12 through suitable gearingand a belt drive from an electric motor 13. A lever 14 is pivotallymounted at 15 and arranged with one end in contact with the periphery ofthe cam member 10. The opposite end of the lever 14 has a forked pivotconnection with the lower end of the hollow valve rod 65 and a bracket11 connects the same also to the innermost valve rod 51. With thisarrangement movement of the lever 14 will cause simultaneous raising andlowering movements of the cup valve 55 and bell valve 64. The bell valvemember 60 is alternately raised and lowered bya second lever 80pivotally mounted at 8| with one end in contact with the periphery ofthe cam member 1|. The opposite end of the lever 60 has a forked pivotconnection with the lower end of the hollow rod 6|. The cam members 10and 1| have their cam surfaces shaped and relatively arranged ontheshaft 12 to effect a cyclic movement of the cup valve 65 and bell valves66 and 64. With the arrangement of the parts shown in Fig. 6, the cupmember 55 and bell valves 60 and 64 are in their upper positions, thecup membei having just been raised to its upper position to dam thepellet flow from the chamber 50 and the valve 64 closed after havingdelivered pellets from the chamber 59 to the pipe 66. The pelletspreviously discharged while the valve 55 is in its lower positionaccumulate in the bottom of th e chamber 52 and the valve 60 is about toopen tq allow this pellet accumulation to drop into the chamber 59, thebottom outlet of which is now closed y the valve 64. The pellets dropinto the chamb F59 and the valve 60 is then moved to its top closingposition, after which the cup member 55 and valve 64 are simultaneouslymoved to their lower positions. The opening movement of the valve 64permits the pellets in the chamber 59 to drop into the discharge pipe66, while the descent of the cup member permits a new batch of pelletsto flow over its periphery and accumulate on the 6 bottom of the chamber52. The parts are proportioned and timed to minimize the possibility ofany pellets becoming jammed between the valves 60 and 64 and theirrespective seats, while the cup member 55 is arranged so that it doesnot actually seat on any surface. Any upward movement of the column ofpellets in the sleeve 53 during the rising movement of the cup member 55is absorbed in the expansion chamber 50 by the movement of the pelletsinto the available space therein.

To insure that no pellets will be accidentally displaced and fall overthe edge of the valve member 55 when the latter is in its upper or flowdamming position, an annular shroud or shield I05 may be arranged tocontact with the peripheral edge of the valve member in that position.The shroud is preferably of oppositely flaring vertical cross-sectionwith its minimum diameter portion of the same diameter as the valvemember peripheral edge, to avoid binding of the parts. The dependingoutlet 5| serves as a support for a vertically adjustable ring I06connected by flexible supporting chains I01 to the shroud member I65. Asthe valve member moves upwardly it enters the lower flared section ofthe shroud, and contacts therewith in its upper position. If any pelletsshould be caught between these parts, the flexible support of the shroudpermits it to be moved upwardly by the valve member.

The discharge pipe 66 is connected through an expansion joint to asecond inclined pipe 86 leading to a box 81 at the foot of an elevatorcasing 88. The box 81 opens into'the elevator casing and is providedwith openings through which pellets can be added or taken from thesystem. The elevator casing 88 is of welded gas mass of refractory heattransfer material.

heating gases flow upwardly through the mass in tight construction, andencloses an elevator 33, indicated as being the slow speed continuousbucket type having overlapping buckets which are partly fllled withpellets at the normal rate of pellet circulation. The elevator is drivenby an electric motor 90 having a drive connection with the elevatorheadshaft. The buckets empty into a vertical discharge pipe SI which hasits lower end opening into an inclined pipe 82, connected through anexpansion joint 33 to the inlet pipe I6. With this arrangement asubstantially continuous circulation of the heat transfer material ismaintained externally of the fluid heater between the bottom dischargeopening 31 and the top inlet pipe IE, so that the mass or column of heattransfer material within the chambers I2 and I3 and throat I4 willdescend at a predetermined rate.

To avoid contamination of the outgoing fluids by any dust and pelletfragments formed during the circulation of the pellets, the heattransfer mat'erial entering through the inlet pipe I6 is preferablysubjected to a scavenging effect by a controllable portion of theheating gases leaving the chamber I2 through the aiixiliary gas outletconduit 20. The lower portion of the conduit 20 is arranged to form anextension of the inlet pipe I6, as shown 'inFigs. 2 and 3. The lowersection .of the conduit is of rectangular crosssection having aninclined bottom 35 and a laterally flared end 85; The bottom 95 isextended I beyond the end 36 to insure a horizontal; travel of theentering pellets in contact with the outgoing gases. The upper portionof the pipe 20 'is of circular cross-section and extends externally to acyclone separator 98 having a bottom outlet 33 for separated solidmaterial and a vent pipe IIIiI controlled by a valve IllI for dischargeof the gases. With this arrangement the valves I8 and II can beregulated either manually or automatically to control the portion of theheating gases leaving the upper chamber I2 through the auxiliary outlet20, and thus maintain the gas velocity conditions necessary to securethe desired scavenging effect on the entering heat transfer material.

In. the normal operation of the described apparatus the heating gasesgenerated in the combustion chamber 25 enter the chamber I2 through theinterstices of the pellets in the gas inlets 32 under a predeterminedpressure, and are substantially uniformly distributed throughout thehorizontal area of e adjacent portion of the The intimate contact withthe descending heat transfer material which reaches its maximumtemperature at the level of the heating gas inlet. The heat transfermaterial continues its descent through the throat passage I4 into thechamber I3. The fluid to be heated, such as air, steam, or other gas orvapor, enters at a predetermined temperature and pressure through thesupply pipe 39 and inlet chamber 38 and flows through the annular screen35 into the lower end of the heat transfer material in the chamber I3,passing upwardly through the interstices in the material in intimatecounterflow contact with the descending pellets. The entering gas is ata relatively low temperature to insure a low discharge temperature forthe pellets which will provide a.

. high thermal efliciency, lessen thermal shock on the pellets, andpermit safe handling of the pellets by the pressure-tight feeder andelevator. The fluid to be heated reaches its maximum temperapheres inthe chambers I2 and I3 can be avoided by maintaining-predeterminedrelative pressures in the two chambers to provide a zero fluid -flowthrough the throat I4. Pressure taps I02 and I" are indicated formeasuring the pressure differential across the throat, and variations inthis condition from a predetermined standard are utilized to control theposition of the valves II and IIII and thereby the gaseous pressure inthe chamber I2 to control the relative pressures in the two chambers.The return of the pellets through the feeder and elevator to the inletpipe I6 has been previously described.

While the feeder valve operating mechanism described is normallyoperated to complete a cycle in a relatively few seconds, and thusprovide a substantially continuous discharge of pellets from the outlet31 and downward movement of the pellet column in the chambers I2 and I3,the high rate of heat transfer in the chamber I3 in conjunction with theperiodic dwell of the pelletsin the chamber even with the rapid cycle offeeder operation described will result in a slight variation in theheated fluid outlet temperature. While such temperature variation may benegligible for most uses of the invention, in some cases a uniform finaltemperature ofthe heated fluid may be important.

A continuous discharge of pellets from the outlet 31 while maintainingthe feeder under pressure is provided by the modified feeder mechanismshown in Fig. 8. In this construction the outlet pipe 31 has an inclinedlower section 31' in which a vibrating feeder unit I I0 is incorporated.The flow area of the inclined pipe section 31' is reduced by a plate IIItherein restricting the pellet flow to one side of the pipe sectionbelow which a horizontally extending vibrating plate H2 is located. Thevibrating plate is supported and actuated by an electrically operatedvibrator unit H3 in a fluid tight casing Ill. The vibrating plate II2extends into the pipe 31' for a distance sufficient to cause the pelletstream to assume an angle of repose thereon and stop the pellet flowwhen the plate H2 is stationary. In operation the pellets continuouslydischarge from the inner end of the plate H2 at a rate depending uponthe vibrating frequency and drop into an expansion chamber having avolumetric capacity sufficient to provide an expansion space above thenormal level of pellets therein. The pellets periodically discharge fromthe chamber 50' through the outlet pipe 5| and feeder mechanismpreviously described. With this feeder construction, the pellet columnwill continuously descen; through the chambers I2 and I3 at acontrollable rate.

While a single fluid heater unit of the character illustrated in Figs.2-7 is capable of continuous operation at relatively high capacities toheat a fluid passed through the chamber I3 to a high temperature, stillhigher fluid final temperatures can be attained by the multiple unitarrangement illustrated in Fig. 1. The fluid heater units A and B showntherein are of similar construction, each having superposed heating andcooling chambers I2 and I3 respectively connected by a throat I4,

with the pellet mass or column circulated there- 7 through by apressure-tight feeder and elevator,

all as shown in Figs. 2-7 or Fig. 8.

In accordance with my invention, the fluid heater A is utilized to heatone of the combustion constituents, either fuel or an oxygen-containinggas, such as air, for the combustion chamber of the fluid heater B, to ahigh temperature to substantially increase the maximum temperature ofthe heating gases generated in the heater B. In view of thesubstantially greater combustion air requirements, it is more efficientto preheat the air than the fuel to be used in heater B. With such anarrangement and all or a major portion of the combustion aircontinuously preheated to a uniform or substantially uniform temperaturesubstantially above the fuel ignition temperature, the temperaturemaintained in the combustion chamber of the heater B will :beconsiderably ,in excess of the maximum temperature obtainable in heaterA. The pellets entering the lower chamber l3 of the heater B willconsequently be at a substantially higher temperature than the pelletsat the same location in the fluid heater A, and thus correspondinglyincrease the flnal temperature of the fluid heated in the heaterB. Thefluid heated in the heater B may be the same or different from the fluidheated in the heater A. By way of example and not of limitation, in Fig.1 I have indicated an arrangement for superheating steam to a hightemperature in the heater 13. Air at room temperature is supplied to theheater A through the pipe 39 and ascends through the pellet mass in thelower chamber i3, being continuousiy heated to a uniform temperature,such as 2000 F., before leaving through the fluid outlet pipe 44. Theair so heated is delivered to the combustion air inlet pipes 30 of theheater B, the parts contacting with the high temperature air being madeof suitable heat resistant material. The high temperature combustion airso supplied mixes with the fuel or combustible mixture entering thecombustion chamber of the heater B and a substantial increase incombustion chamber temperature results. For example, combustion chambertemperatures of over 3000 F. can be easily secured. The saturated steamto be superheated enters the heater B through the fluid inlet pipe 39,flows upwardly through the heated pellet mass in the lower chamber, andin a highly superheated condition, such as at 2500-3000 F., leavesthrough the outlet conduit 44. A high thermal efliciency is attained andcontinuous operation of the units is insured by the reduction of thepellet temperature by the entering low temperature fluid in each unit toa temperature at which the pellets can be safely handled by the feederand elevator mechanism and pellet breakage minimized.

The multiple unit arrangement described is not limited to the two unitarrangement shown, but any number of such units can be interconnected asshown to obtain operating temperatures up to the permissible usetemperature limits of the pellets and the refractory materials used inthe fluid heater unit construction. In such arrangements, the fluid tobe finally heated is heated in the last heater unit of the series andthe preceding units are utilized for heating a combustion constituent,such as fuel or air, which is used in the combustion chamber of asubsequent unit of the series. My invention also contemplates thepreheating of both the fuel and air constituents peratures heretoforeconsidered unattainable with such fuels. The material dischargemechanisms shown in Figs. 6-9 are disclosed and claimed in my copendingdivisional application, Serial No. 625,239, flied October 29, 1945.

I claim:

1. The method of heating a fluid to a high temperature which comprisesmaintaining a flow of a fluent mass of heat transfer material throughheating and cooling zones in a fluid heater, heating said mass of heattransfer material to a high temperature while in said heating zone,cooling the heated mass of heat transfer material while in said coolingzone by heat transfer to a fluid combustion constituent flowing throughsaid cooling zone in heat transfer relation with said heat transfermaterial, maintaining a flow of a second fluent mass of heat transfermaterial through heating and cooling zones in a second fluid heater,heating the second mass of heat transfer material to a high temperaturewhile in said second heating zone by heating gases generated by acombustion process utilizing the heated fluid combustion constituentfrom said first cooling zone, and cooling the mass of heated heattransfer material while in said second cooling zone by heat transfer toa fluid flowing through said second cooling zone in heat transferrelation with said heat transfer material.

2. The method of heating a fluid to a high temperature which comprisesmaintaining a flow of a fluent mass of heat transfer material downwardlythrough superposed heating and cooling zones in a fluid heater, heatingsaid mass of heat transfer material to a high temperature while in saidheating zone, cooling the heated mass of heat transfer material while insaid cooling zone by heat transfer to a fluid combustion constituentflowing through said cooling zone in direct contact with said heattransfer material, maintaining a flow of a second fluent mass of heattransfer material downwardly through superposed heating and coolingzones in a second fluid heater, heating the second mass of heat transfermaterial to a high temperature while in said second heating zone byheating gases generated by a combustion process utilizing the heatedfluid combustion constituent from said flrst cooling zone, and coolingthe mass of heated heat transfer material while in said second coolingzone by heat transfer to a fluid flowing through said second coolingzone in direct contact therewith.

3. The method of heating a fluid to a high temperature which comprisesmaintaining a substantially continuous flow of a fluent mass of heattransfer material downwardly through superposed heating and coolingzones in a fluid heater, heating said mass of heat transfer material toa high temperature while in said heating zone, cooling the heated massof heat transfer material while in said cooling zone by heat transfer toa fluid combustion constituent flowing through said cooling zone incounterflow direct contact with said heat transfer material, maintaininga substantially continuous flow of a second fluent mass of heat transfermaterial downwardly through superposed heating and cooling zones in asecond fluid heater, heating the second mass of heat transfer materialto a high temperature while in said second heating zone by heating gasesgenerated by a combustion process utilizing the heated fluid combustionconstituent from said first cooling zone, and cooling the mass of heatedheat transfer material while in said second cool- 1! ing zone by heattransfer to a fluid flowing through said second cooling zone incounterflow direct contact with said heat transfer material.

4. The method of heating a fluid to a high temperature which comprisesmaintaining a flow of a fluent mass of heat transfer material downwardlythrough superposed heating and cooling zones in a fluid heater, heatingsaid mass of heat transfer material to a high temperature while in saidheating zone, cooling the heated mass of heat transfer material while insaid cooling zone by heat transfer to a stream of air flowing throughsaid cooling zone in direct contact with said heat transfer material,maintaining a flow of a second fluent mass of heat transfer materialdownwardly through superposed heating and cooling zones in a secondfluid heater, heating the second mass of heat transfer material to ahigh temperature while in said second heating zone by heating gasesgenerated by a combustion process utilizing the heated air from saidfirst cooling zone, and cooling the mass of heated heat transfermaterial while in said second cooling zone by heat transfer to a fluidto be heated flowing through said second cooling zone in direct contactwith said heat transfer material.

5. Fluid heating apparatus comprising a pair of fluid heater units, eachof said units having walls deflning an upper chamber and a lower chamberconnected thereto, a continuous fluent mass of refractory heat transfermaterial in said upper and lower chambers, and means providing a flow ofsaid heat transfer material downwardly through said chambers, means forheating the heat transfer material in the upper chamber of one of saidheater un ts, means for passing a fluid combustion constituent throughthe lower chamber of said heater unit in heat transfer relation with theheated heat transfer material therein, means for heating heat transfermaterial in the upper chamber of the second heater unit by heating gasesfrom a combustion process utilizing the heated fluid combustionconstituent from said first heater unit, and means for passing a fluidto be heated through the lower chamber of said second heater unit inheat transfer relation with the heated heat transfer material therein.

6. Fluid heating apparatus comprising a pair of fluid heater units, eachof said units having walls defining an upper chamber and a lower chamberconnected thereto, a continuous fluent mass of refractory heat transfermaterial in said upper and lower chambers, and means providing a flow ofsaid heat transfer material downwardly through said chambers, means forheating the heat transfer material in the upper chamber of one of saidheater units, means for passing a fluid combustion constituent throughthe lower chamber of said heater unit in direct contact with the heatedheat transfer material therein, means for heating the heat transfermaterial in the upper chamber of the second heater unit by heating gasesfrom a combustion process utilizing the heated fluid combustionconstituent from said first heater unit. and means for passing a fluidto be heated through the lower chamber of said second heater unt indirect contact with the heated heat transfer material therein.

7. Fluid heating apparatus comprising a pair of fluid heater units, eachof said units having walls'defining an upper chamber, a lower chamber,and a throat passage of reduced cross-section between said upper andlower chambers, a continuous fluent mass of refractory pellets in saidupper and lower chambers and throat passage, and means providing asubstantially continuous flow of pellets downwardly through saidchambers and throat passage, means for heating the pellets in the upperchamber of one of said heater units, means for passing a fluidcombustion constituent through the lower chamber of said heater unit incounterflow heat transfer relation with the heated pelets therein, meansfor heating pellets in the upper chamber of the second heater unit byheating gases from a combustion process utilizing the heated fluidcombustion constituent from said flrst heater unit. and means forpassing a fluid to be heated through the lower chamber of said secondheater unit in counterflow heat transfer relation with the heatedpellets therein.

8. A fluid heater comprising a wall structure defining a chamber, afluent mass of refractory heat transfer material in said chamber, meansfor introducing a stream of heating gases into said chamber in directcontact with said heat transfer material, means for effecting a flow ofheat transfer material downwardly through said chamber comprising anelevating means arranged to receive heat transfer material from thelower end of said chamber and a conduit receiving heat transfer materialfrom said elevating means and returning the same to the upper part ofsaid chamber above the level of heat transfer material therein, and aheating gas outlet in the upper part of said chamber constructed andarranged to cause the outgoing heating gases to scavenge the enteringheat transfer material of underslze particles.

9. A fluid heater comprising a wall structure defining a chamber, afluent mass of refractory heat transfer material in said chamber, meansfor introducing a stream of heating gases into said chamber in directcontact with said heat transfer material, means for effecting a flow ofheat transfer material downwardly through said chamber comprising anelevating means arranged to receive heat transfer material from thelower end of said chamber and a conduit receiving heat transfer materialfrom said elevating means and returning the same to the upper part ofsaid chamber above the level of heat transfer material therein, aheating gas outlet in the upper part of said chamber constructed andarranged to cause the outgoing heating gases to scavenge the enteringheat transfer material of undersize particles, and a gas and solidseparator receiving heating gases from said gas outlet.

10. A fluid heater comprising a wall structure defining a chamber, afluent mass of refractory pellets in said chamber, means for introducinga stream of heating gases into said chamber in direct contact with saidpellets, means for effecting a flow of pellets downwardly through saidchamber comprising an elevating means arranged to receive pellets fromthe lower end of said chamber and a conduit receiving pellets from saidelevating means and returning the same to the upper part of said chamberabove the level of pellets therein, and a heating gas outlet in theupper part of said chamber constructed and arranged to cause theoutgoing heating gases to scavenge the entering pellets of undersizeparticles.

11. A fluid heater comprising a wall structure defining a chamber, afluent mass of refractory heat transfer material in said chamber, meansfor introducing a stream of heating gases into said chamber in directcontact with said heat 13 transfer material, means for effecting a flow01' heat transfer material downwardly through said chamber comprising anelevating means arranged to receive heat transfer material from thelower end of said chamber and a conduit receiving heat transfer materialfrom said elevating means and returning the same to the upper part ofsaid chamber above the level of heat transfer material therein, aheating gas outlet in the upper part of said chamber constructed andarranged to cause the outgoing heating gases to scavenge the enteringheat transfer material of undersize particles, a gas and solid separatorreceiving heating gases from said gas outlet, a second heating gasoutlet from said chamber, and damper means for regulating thedistribution of heating gases to said outlets.

CHARLES L. NORTON, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

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